EGFR-dependent migration of glial cells is mediated by reorganisation of N-cadherin

Abstract

Receptor tyrosine kinases of the EGFR family exert their various effects on cellular function through the formation of different dimeric receptor complexes. To investigate the functional impact of EGFR-HER2 heterodimers on migration of glial tumour cells, we stably transfected different HER2 constructs, including a constitutively active (HER2VE) and a dominant-negative (HER2VEKA) receptor, in the EGFR-overexpressing human glioma cell line LN18. Interference of EGFR activation through HER2VEKA inhibited cellular migration, whereas EGFR activation through HER2VE increased migration. These results were corroborated by inhibition of EGFR-HER2 signalling with tyrosine kinase inhibitors, because only the blocking of both receptors in HER2VE-cells with the bi-specific inhibitor AEE788 downregulated migration to levels comparable with those in HER2VEKA cells. The non-migratory phenotype was mediated through upregulation of N-cadherin and its recruitment to the cell membrane in HER2VEKA cells; downregulation of N-cadherin by RNAi restored migration in HER2VEKA cells and N-cadherin was also downregulated in migrating HER2VE-cells. Downregulation of N-cadherin levels in the plasma membrane was accompanied by a direct interaction of the EGFR-HER2 and N-cadherin-beta-catenin complexes, leading to tyrosine phosphorylation of beta-catenin. These results indicate that HER2 affects glial-cell migration by modulating EGFR-HER2 signal transduction, and that this effect is mediated by N-cadherin.